The invention concerns a winding machine for winding solenoid-shaped coils having band-shaped conductors, comprising a winding means that can hold a circular cylindrical coil core of a coil to be wound, and a winding drive that can turn a coil core, held in the winding means, about a winding axis W, wherein the winding means can be moved in a first direction A using an axial drive, the direction A preferably extending approximately parallel to the winding axis W.
U.S. Pat. No. 4,870,742 discloses a winding machine of this type.
Solenoid-shaped coils are used to generate strong magnetic fields which are required e.g. in nuclear magnetic resonance (NMR) spectroscopy or magnetic resonance imaging (MRI). A conductor is wound on them, with several layers of conductors being disposed on top of each other. The individual layer is helically wound.
Conductors containing superconducting material are used to increase the magnetic field strength. The use of HTS materials (high-temperature superconducting materials) is thereby particularly desired, since these can carry a higher current than conventional superconductor materials under certain temperature and magnetic field conditions of use. The typical design of high-temperature superconductors is a band shape. Band-shaped conductors have an approximately rectangular cross-section, with a first side (long side) being considerably longer than a second side (short side). Typical side-width ratios are 10:1 and more. In case of high-temperature superconductors containing bismuth, the superconducting material is thereby typically present in the form of filaments which are surrounded by a silver matrix.
Many superconducting materials, in particular HTS materials, break easily under mechanical load, in particular during winding of a coil. When an excessive number of superconducting filaments in a band-shaped conductor break, the conductor becomes useless, since the current carrying capacity that can be technically utilized decreases. Bending through the short side is particularly detrimental for band-shaped conductors with brittle superconducting material.
U.S. Pat. No. 4,870,742 describes winding a solenoid-shaped coil with band-shaped conductors by guiding a band-shaped conductor to a rotating coil core using stationary guiding means. The coil core is axially carried along in one layer in correspondence with the winding advance. This prevents bending of the conductor through the short side due to winding advance in the layer.
The winding machine in accordance with U.S. Pat. No. 4,870,742 is well suited to produce a solenoid-shaped coil with only one layer. However, for magnet coils, several continuously connected layers are desirable. For changing from one finished layer to a further overlying layer, the pitch of the helical winding must be reversed. The changed pitch strongly bends the band-shaped conductor through the short side and the conductor is in danger of being damaged.
In contrast thereto, it is the object of the present invention to provide a winding machine for winding a solenoid-shaped coil with several layers of band-shaped conductor without damaging the band-shaped conductor, in particular, when the band-shaped conductor contains brittle, superconducting material.